Percutaneous angioplasty such as PTA (Percutaneous Transluminal Angioplasty) or PTCA (Percutaneous Transluminal Coronary Angioplasty) is a therapy in which a narrow part or an occluded part generated in a vascular lumen is removed, and a procedure for recovering or improving blood flow in a coronary artery or a peripheral blood vessel.
In such a percutaneous angioplasty, catheters formed of a medical tube are used. In usual, the catheter is advanced while a route (blood vessel) is selected, until it reached a narrow part to be treated. In addition, for example, in a case of a balloon catheter, after the catheter reaches a part to be treated, a pointed end of the catheter passes through a narrow part and a balloon, which is disposed around the pointed end, dilates the narrow part.
This balloon has desirably a physical property in which it is easily folded to a small diameter in order to improve pass characteristic until a narrow part to be treated, and for this end, a thinner film thickness is better. On the other hand, however, it is necessary that the pressure resistance of the balloon is enhanced by providing a uniform and above certain film thickness to the balloon, in order to improve an expansive force of the balloon at the narrow part. In order to make the diameter smaller, it is preferable that the film thickness of the balloon is thinner, however, a balloon having a partially extremely thin (that is, ununiform) film thickness, because of excessive pursuit of thinness, has a deteriorated pressure resistance.
It is desirable, accordingly, that the film thickness of the balloon is made as thinner as possible while the uniformity is kept. For this end, for example, Patent Document 1 discloses a blow-molding method in which a tube, which has been drawn in an axial direction while a balloon part is left, is mounted on a balloon metal mold when a balloon tube is formed.